SUBJECT E. MATERIALS, HARDWARE, PROCESSES

Question 1

1. What is the alloy number of the most commonly used aluminum alloy for aircraft structural use? (AM.I.E.K1)

Answer 1

2024-T

Question 2

2. What is the alloy number of a high strength aluminum alloy that has zinc as an alloying component? (AM.I.E.K1)

Answer 2

7075

Question 3

3. What type of composite material is used when stiffness is the prime requirement? (AM.I.E.K1)

Answer 3

Graphite (carbon).

Question 4

4. What type of composite material is used when toughness is the prime requirement? (AM.I.E.K1)

Answer 4

Kevlar®.

Question 5

5. Why is a piece of steel tempered after it has been hardened? (AM.I.E.K2)

Answer 5

When steel is hardened, it becomes brittle. Tempering removes some of this BRITTLENESS.

Question 6

6. How is steel annealed? (AM.I.E.K2)

Answer 6

It is heated to just above its upper critical temperature until it reaches a uniform temperature throughout, then it is allowed to cool very slowly in the oven.

Heat above critical → soak → slow furnace cool
Soft state

Question 7

7. How is steel hardened? (AM.I.E.K2)

Answer 7

It is heated to its critical temperature and quenched in water, brine, or oil.

Question 8

8. What is meant by tempering steel? (AM.I.E.K2)

Answer 8

The steel is first hardened; then some of the hardness is removed to relieve some of the internal stresses and brittleness.

Question 9

9. What is meant by case hardening? (AM.I.E.K2)

Answer 9

The surface of the metal is hardened by the infusion of carbon or aluminum nitride. The interior of the metal remains strong and tough.

Question 10

10. What are two methods of case hardening? (AM.I.E.K2)

Answer 10

Carburizing and nitriding.

Question 11

11. How is steel nitrided? (AM.I.E.K2)

Answer 11

The steel part is heated in a RETORT in which there is an atmosphere of AMMONIA (a compound of NITROGEN and HYDROGEN). Aluminum, an alloying element in the steel, combines with the nitrogen to form an extremely hard aluminum nitride on the surface of the steel.

Question 12

12. What is the method of solution heat treatment of an aluminum alloy? (AM.I.E.K2)

Answer 12

The metal is hardened by heating it in a furnace to a specified temperature and immediately quenching it in water. It is soft when it is removed from the quench, but as it ages it regains its hardness.

Heat and soak to a temperature range → rapid quench → wait to age = hard

Question 13

13. What is the method of precipitation heat treating of an aluminum alloy? (AM.I.E.K2)

Answer 13

The metal is heated and quenched, then it is returned to the oven and heated to a lower temperature. It is held at this temperature for a specified time, then removed from the oven and allowed to cool in still air. This increases the strength and hardness of the metal. Precipitation heat treating is also called artificial aging.

Question 14

14. What is another name for precipitation heat treatment? (AM.I.E.K2)

Answer 14

Artificial aging.

Question 15

15. Identify and explain the differences between heat-treated and non-heat-treated aluminum alloys. (AM.I.E.K2)

Answer 15

Heat-treated aluminum alloy designations are normally followed with a -T, followed by a number (1–10) that designates the type of heat treat. A common aircraft aluminum alloy is 2024-T3. Heat-treated aluminum is stronger than non-heat-treated aluminum.

Question 16

16. Why is it important that a piece of aluminum alloy be quenched immediately after it is removed from the heat treating oven? (AM.I.E.K2)

Answer 16

Any delay in quenching aluminum alloy after it is removed from the oven will allow the GRAIN STRUCTURE TO GROW enough that INTERGRANULAR corrosion is likely to form in the metal.

Question 17

17. Describe and explain the forces placed on aircraft materials. (AM.I.E.K3)

Answer 17

Tension—A force tending to stretch or elongate the material.
Compression—A force tending to compress or shrink.
Torsion—A twisting force on an object.
Bending—A perpendicular force on the longitudinal axis of an object, causing it to flex or bend. The inner surface of the bend will be in compression and the outer surface of the bend will be in tension.
Strain—The stress on an object which can cause the object to change shape or to become distorted.
Shear—A force that tries to cut or slice through an object. The force is parallel to the material cross section.

Question 18

18. What type of loading should be avoided when using a self-locking nut on an aircraft bolt? (AM.I.E.K4)

Answer 18

A self-locking nut should not be used for any application where there are any rotational forces applied to the nut or to the bolt.

Question 19

19. What determines the correct grip length of a bolt used in an aircraft structure? (AM.I.E.K4)

Answer 19

The grip length of the bolt should be the same as the combined thicknesses of the materials being held by the bolt.

Question 20

20. How tight should the nut be installed on a clevis bolt that is used to attach a cable fitting to a control surface horn? (AM.I.E.K4)

Answer 20

The nut on a clevis bolt should not be tight enough to prevent the clevis bolt from turning in the cable fitting and the horn.

Question 21

21. What bolt is described by this number: AN6-14A? (AM.I.E.K4)

Answer 21

AN6 = Hex head bolt, 6/16 (3/8) inch diameter.
14 = Length = 1-4/8 (1-1/2) inch long.
A = The shank is not drilled for a cotter pin.

Question 22

22. What is indicated by a triangle on the head of a steel bolt? (AM.I.E.K4)

Answer 22

This is a close tolerance bolt.

Question 23

23. What is a correct application for self-tapping sheet metal screws on an aircraft? (AM.I.E.K4)

Answer 23

They may be used to hold nonstructural components onto the aircraft.

Question 24

24. How can you tell when a self-locking nut must be discarded? (AM.I.E.K4)

Answer 24

When you can screw the nut onto a bolt without having to use a wrench.

Question 25

25. What is a channel nut? (AM.I.E.K4)

Answer 25

A series of nuts mounted loosely in a channel that is riveted to the aircraft structure. You can install screws in a channel nut without having to hold the nut with a wrench.

Question 26

26. Of what two materials are cotter pins made? (AM.I.E.K4)

Answer 26

Low-carbon steel and corrosion-resistant steel.

Question 27

27. What is the smallest size cable that is allowed to be used in the primary control system of an aircraft? (AM.I.E.K4)

Answer 27

1/8-inch diameter.

Question 28

28. What type of control cable must be used when pulleys are used to change the direction of cable travel? (AM.I.E.K4)

Answer 28

Extra-flexible cable (7 × 19).

Question 29

29. What is the purpose of safety wire? (AM.I.E.K5)

Answer 29

To prevent a nut, bolt, or other component from loosening.

Question 30

30. After torquing a castellated nut, can the nut be loosened to align with the hole in a bolt for installing the cotter pin? (AM.I.E.K5)

Answer 30

No. Never over-torque or loosen a torqued nut to align safety wire or cotter pin holes. The nut should be torqued to the minimum torque, and then tightened to align with the safety hole, without exceeding the maximum torque.

Question 31

31. What kind of measuring instrument is used to measure the runout of an aircraft engine crankshaft? (AM.I.E.K6)

Answer 31

A dial indicator.

Question 32

32. What measuring instruments are used to measure the fit between a rocker arm shaft and its bushing? (AM.I.E.K6)

Answer 32

The outside diameter of the shaft is measured with a micrometer caliper. The inside of the bushing is measured with a telescoping gauge and the same micrometer caliper.

Question 33

33. In what increments can a vernier micrometer caliper be read? (AM.I.E.K6)

Answer 33

One ten thousandth (0.0001) inch.

Question 34

34. What is an advantage of a vernier caliper over a micrometer caliper? (AM.I.E.K6)

Answer 34

The range of a vernier caliper is far greater than that of a micrometer caliper.

Question 35

35. What precision tool is used to measure piston ring side clearance? (AM.I.E.K6)

Answer 35

Thickness gauge.

Question 36

36. What precision tools are used to measure the inside diameter of a cylinder? (AM.I.E.K6)

Answer 36

A telescoping gauge and a micrometer caliper.

Question 37

37. What precision tools are used to measure the inside diameter of a small hole? (AM.I.E.K6)

Answer 37

A small hole gauge and a micrometer caliper.

Question 38

38. What kind of solder is recommended for soldering electrical wires? (AM.I.E.K7)

Answer 38

60/40 resin-core solder.

Question 39

39. What is the function of the flux used in soldering? (AM.I.E.K7)

Answer 39

Flux covers the cleaned and heated metal to keep oxygen away from it so oxides cannot form. Oxides keep the solder from adhering to the surface of the metal.

Question 40

40. What are the three most common types of torque wrenches? (AM.I.E.K8)

Answer 40

Deflecting beam, dial indicating, and micrometer setting types.

Question 41

41. Where would an aviation mechanic find the appropriate hardware specifications for use on a particular aircraft? (AM.I.E.K9)

Answer 41

In the aircraft manufacturer’s illustrated parts catalog (IPC).

Question 42

42. Where would an aviation mechanic find the material specifications for structural repairs on an aircraft? (AM.I.E.K9)

Answer 42

In the aircraft manufacturer’s structural repair manual (SRM).

Question 43

43. Why is it very important that the surface of a piece of clad aluminum alloy not be scratched? (AM.I.E.K9)

Answer 43

The pure aluminum used for the cladding is noncorrosive, but the aluminum alloy below the cladding is susceptible to corrosion. If the cladding is scratched through, corrosion could form.

Question 44

44. What is the preload value when torquing a nut? (AM.I.E.K10)

Answer 44

Preload is the force or torque required to overcome the friction between the threads on the nut and the threads of the bolt prior to the nut contacting the mating surface.

Question 45

45. How is the preload value used when torquing a nut? (AM.I.E.K10)

Answer 45

The preload torque is added to the specified torque to obtain the required setting on the torque wrench.

Question 46

46. How can the material of a bolt be identified? (AM.I.E.K11)

Answer 46

By manufacturer markings that are on the bolt head.

Question 47

47. How is the welding flux removed from a piece of aluminum that has been gas-welded? (AM.I.E.K12)

Answer 47

It should be removed by scrubbing it with hot water and a bristle brush.

Question 48

48. What are the visual characteristics of a good weld? (AM.I.E.K12)

Answer 48

A good weld is uniform in width; the ripples are even and well feathered into the base metal and show no burn due to overheating. The weld has good penetration and is free of gas pockets, porosity, or inclusions.

Question 49

49. What are the visual characteristics of a bad weld? (AM.I.E.K13)

Answer 49

A bad weld has irregular edges and considerable variation in the depth of penetration. It often has the appearance of a cold weld.

Question 50

50. What must be done to a welded joint if it must be rewelded? (AM.I.E.K14)

Answer 50

All traces of the old weld must be removed so the new weld will penetrate the base metal.

Question 51

51. What is meant by normalizing a piece of steel after it has been welded or machined? (AM.I.E.K14)

Answer 51

Normalizing removes stresses that are locked into the material by welding or machining.

Question 52

52. How is a steel structure normalized after it has been welded? (AM.I.E.K14)

Answer 52

Heat the steel structure to a temperature above its critical temperature and allow it to cool in still air.

Question 53

53. What determines the size of tip that is to be used when gas-welding steel? (AM.I.E.K14)

Answer 53

The thickness of the material being welded. The size of the tip orifice determines the amount of flame produced and thus the amount of heat put into the metal.